For example, suction sleeve rolls in the paper-making industry are used as exposed to white water and must therefore have high corrosion resistance and high corrosion fatigue strength. The materials which are outstanding in these characteristics include ferrite-austenite duplex stainless steel, precipitation-hardened stainless steel and the like, but these materials are generally poor in cuttability. Since these materials are especially poor in machinability with drills, they are extremely difficult to cut with twist drills and are actually not usable.
Accordingly, martensitic stainless steels, typical of which is JIS SCSl material, are widely used for paper-making suction rolls because these steels are excellent in machinability with drills and inexpensive. Nevertheless, these materials have the problem of being low in stability when used for machine members. For example, they are not fully satisfactory in corrosion resistance and fatigue strength for use in corrosive environments containing chlorine ion. Especially when used under conditions involving repeated stresses, the material deteriorates early, permitting failures such as a break of rolls.
In the case of paper mills, in particular, the operation is conducted in recent years at a higher speed, at a lower pH value and at a higher concentration of S.sub.2 O.sub.3.sup.2- ions and is therefore carried out in a more corrosive environment due to the presence of white water. Thus, it is required that the material to be used be improved in corrosion resistance and corrosion fatigue strength.
The present invention provides a novel material fulfilling this requirement.